Technical Abstract:
Marek’s disease virus (MDV) infected cells express a viral ribonucleotide reductase (RR) that is distinguishable from that present in uninfected cells by monoclonal antibody T81. Open reading frames UL39 and UL40 of the MDV genome encode the large (RR1) and small (RR2) subunits of RR enzyme, respectively. RR1 and RR2 form an active holoenzyme and both subunits are necessary for enzyme activity. RR1 is predicted to comprise 860 amino acids (aa), and RR2 is predicted to be 343 aa in length. MDV RR is expressed abundantly in the cytoplasm of MDV infected duck embryo fibroblasts and Mab T81 reacts with 45 strains of all 3 MDV serotypes indicating that it is a highly conserved protein among MDV strains. MDV RR is also highly expressed in lymphoid organs and feather follicles of the infected chickens. The persistent expression of RR in infected chickens suggests an important role in MDV pathogenesis. Using recombinant DNA technology we have generated a mutant MDV in which RR1 was deleted. Deletion of RR1 did not impair viral growth in vitro and in vivo pathogenesis studies are in progress.